Flexural behavior and bearing capacity calculation of prestressed composite box girders with corrugated high-strength webs and UHPC slabs

To enhance the spanning capacity and crack resistance of composite box girders with corrugated webs, a novel composite box girder featuring corrugated high-strength steel webs and UHPC slabs was proposed prestressed with both internal and external tendons. To investigate the flexural performance, two specimens with different concrete strength and thickness were tested. Test results indicated that both composite girders with high-strength concrete and UHPC exhibited a flexural failure mode characterized by complete cracking of the bottom slab, cracking on the lower surface of the top concrete slab, and crushing on its upper surface. However, the UHPC slabs showed a smaller extent and severity of crushing. Additionally, the specimen with UHPC slabs demonstrated superior initial stiffness and ductility. Subsequently, an ABAQUS-based finite element model was developed for prestressed composite box girders with corrugated high-strength steel web and UHPC slabs. After validated against experimental results, the model was used to study the influence of height, yield strength and thickness of corrugated steel web, yield strength of reinforcement, and initial prestressing level on flexural behavior. The results revealed that increasing the height of corrugated steel webs enhanced both the crack stiffness and the flexural capacity. Increasing the yield strength and thickness of the corrugated steel webs had a relatively minor effect on the initial stiffness but improved the flexural capacity to a certain extent. A higher initial prestressing stress led to earlier failure of the UHPC top slab, resulting in a slight reduction in both the ultimate capacity and ductility. The residual tensile stress in the UHPC bottom slab remained above 2 MPa at the peak load, and a triangular distribution of tensile stress was observed in the corrugated steel web near the lower steel flange, which could contribute to the overall flexural capacity. Finally, based on plastic theory, a calculation formula for the flexural bearing capacity of prestressed composite box girders with corrugated high-strength steel web and UHPC slabs was derived considering the contribution of UHPC slab and corrugated high-strength steel web. The calculated results showed good agreement with the finite element simulation results, providing theoretical support for the design and application of such composite girders.